Crimping tools using interchangeable accessory dies are known in the art. As will be appreciated by one of ordinary skill in the art, crimp die sets are used in various fields for various purposes. One particularly applicable field involves those environments when crimping is required for grounding metal surfaces. Such environments include grounding steel “I”-beams in construction and steel supports for solar panels in solar farms. Other environments include situations such as grounding steel street grates or steel ladders in sewer manholes, etc. Typically, these environments involve metal substrates having thicknesses of ⅛ inch to ⅞ inch. To these metal substrates, a grounding connector and grounding wire are crimped together. The composite is then adapted to take ground fault energy and the like from the substrate through the connector to the wire and then safely to ground.
For these types of environments, the art has developed particularized crimp die sets and methods. For example, when installing electrical connectors and ground wires to metal substrates, it is particularly imperative that the materials stay connected even under stress or otherwise the ground fault protection is lost. To this end, Underwriter's Laboratories has promulgated the UL467 Standard for grounding connectors that specifies a minimum “pull off” value. As will be appreciated, the pull off value is the amount of stress (pounds) that is required to pull the grounding member off of the metal substrate. By requiring a minimum pull off value be met, UL-approved products can help assure that grounding wires and the like stay attached to the metal substrates through the range of stresses that may be encountered in the environment, thereby maintaining the protection against ground faults.
The art generally recognizes that structural steel and other flat surfaces are often generally smooth in texture. A problem with smooth surfaces is that it is difficult to simply squeeze a connector onto the smooth surface and expect it to remain adhered under even minimal stress. To combat this adhesion problem, the art uses “knurling” dies to condition the surface of the metal substrate. “Knurling” dies are a set of dies that include a field of raised features that will deform the surface(s) of substrate under pressure to leave the surface(s) textured. Typical, the knurls (raised features) are pyramidal in shape. Knurling leaves the surface textured and thus able to form more meaningful and lasting connections when crimped together with other materials. Knurling is carried out using a crimp tool that is loaded with right and left die members (a die set). Once loaded, the crimp tool is positioned such that its jaws accept the connection area of the substrate and then operated to squeeze the metal substrate under force (up to 12 tons) between the die members. The die members in turn displace and deform the metal substrate surface with an imprint of the topography of the die member faces. Dies come in different sizes and shapes and each configuration has its own “die number.” The die number is specific to the die set and is a universally recognized classification system for dies.
Notably, the connectors to be crimped to the metal substrates have been tested by UL to meet the pull off value requirement. The die index number for the die set used with the connector in passing the tests that are required for UL approval plays an important role. In order to comply with the standard, the same die number must be used in the field when crimping the connectors to substrates (to assure that the minimum pull off value is achieved).
In connection with complying with the UL standard, the instructions for most electrical connectors identify the die index to be used in crimping the connectors to the metal substrate. An issue arises when an electrical inspector is inspecting a work site and needs a way to identify if the connections are complying with the UL standard by employing the correct die index. Presently, the art has evolved to the use of a second die set having a mirror-image impression of the die index number in the face of the die members. The provision of the die number recesses in the die members allows the crimp tool to be reloaded with the second die set and activated a second time to squeeze the metal, typically copper, connectors such that the second die set members deform the metal to the point that it is accepted into the impressions during crimping, thereby embossing the die number raised and visibly discernible on the connector body after crimping. An inspector can then visually see the die index number and confirm that the correct die set was used in crimping the grounding connector and wire to the metal substrate sufficient to meet the UL standard during his inspection.
As will be appreciated, the current state of the art of crimp tool dies for grounding operations uses two separate die sets to perform the crimping operation. The first die set is used to prepare the surface. The second die set in turn crimps the connector to the surface and embosses a die index number thereon. The process of loading the crimp tool with a first die set to condition the surface of the substrate and engaging the substrate, then removing the tool from the substrate, loading a second die set, repositioning the tool and a connector/wire assembly, and then crimping the connector/wire assembly and substrate together (and leaving a visible die index number on the surface) is time consuming.
Additionally, as will be appreciated, the cost of knurling dies and separate die index dies is expensive as an installer must purchase two crimp die sets for each crimp size, thereby increasing costs and inventory. Not only is additional time required to conduct the crimp operation in switching between the two different crimp die sets, an improper size second die set can accidentally be used, thereby resulting in a poor crimp.
The foregoing highlights some of the problems with conventional crimp die sets. Furthermore, the foregoing highlights the long-felt, yet unresolved need in the art for a crimping method that can be used more quickly and efficiently to meet the requirements for crimping operations in the field. In addition, the foregoing highlights the inventor's recognition of a need in the art for a crimp die set that prepares a crimping surface and embosses an identification number thereon.